1. Field of the Invention
The invention relates to a rolling truck equipped with a transponder for easy identification.
2. Description of the Prior Art
Rolling trucks serve as transport containers and are commonly known as "catering trolleys". They are useful for serving food and beverages to passengers on airplanes. The rolling trucks have a sturdy design and have a container to accommodate the provisions. Normally, the entire container is constructed out of metal, especially the bottom of the container. Castors are located on the front and rear of the bottom side to make it easier to move the rolling truck. Furthermore, the rolling trucks are equipped with a brake gear to lock the castors in place and prevent the container from rolling. The brake gear is engaged when foods or beverages are removed from the container and given to a passenger.
Known rolling trucks have a transponder located at the bottom of the rolling truck. The transponder is equipped with a memory device capable of receiving and transmitting data. The memory holds data assigned to the respective rolling truck and is used in identifying the trucks. The transponder usually does not have its own power source. Instead, it receives the power required for operation from the high-frequency field of a reader as soon as the transponder enters the area of influence of this reader.
When an airplane lands at an airport with rolling trucks, the rolling trucks are unloaded from the airplane, cleaned, washed, and inspected. The inspection determines whether the respective rolling truck can be reused directly, or if repair work will be necessary.
If the rolling truck passes the inspection, the washed rolling truck is transferred to a collecting zone where it is filled with new provisions. If the rolling truck fails the inspection, it is sent to a repair area for repairs. After being repaired, the rolling truck is sent to the collecting zone. In the event repairs are no longer possible, the rolling truck will be put out of service as scrap.
The process thus described can be explained with respect to transponders assigned to each rolling truck. At those places where the rolling trucks enter or leave the areas or zones described above, a coil or inductor of a reader is provided in the floor to act as an antenna. When a rolling truck passes over the reader, a wireless data exchange takes place automatically between the transponder and the reader. It is therefore possible to detect the respective location of each transponder using a centrally located system that is connected to all of the readers. If a rolling truck is being repaired, the type of repair can be entered into the transponders memory. This makes it possible to ascertain, at any point in time, how often a given rolling truck has been repaired and what specific types of repairs have been involved. Analysis of the corresponding data also makes it possible to determine which areas of the rolling trucks are particularly likely to need repairs and consequently where improvements are needed.
If a rolling truck is lost, it is possible, with the help of the system described here, to ascertain the most recent location of the transponder. In addition to the possibilities described, there are many other cases which make it advantageous to use a transponder on a rolling truck.
When a transponder and a reader are used, it is important to keep the distance between the antenna of the reader and the transponder to a minimum, so that enough energy is transmitted to the transponder coil, and data sent by the transponder can be received. With the known rolling trucks, the transponder is located in the floor of the metal container, and the distance between the bottom of the container and the floor is determined by the castors on the rolling truck. The distance is approximately 10 cm.
The outside dimensions of a transponder are determined mainly by the coil used for the inductive transmission. The coil size therefore limits the amount of miniaturization possible. In addition, the bottom of the rolling truck is typically made out of metal. A metal floor greatly reduces the transmitting and receiving power of the transponder due to the absorption of some of the HF energy.
In order to ensure reliable transmission of data between the reader and transponder, due to the above factors, comparatively large transponders with large coils are necessary. The typical dimensions of a transponder housing are approximately 10 mm high, 27 mm wide, and 67 mm long.
The following should be taken into account with regard to the arrangement of the transponder on the bottom of the rolling truck. When the rolling trucks are automatically washed or transferred to the collecting zone, or filled with new provisions, the rolling trucks are placed on conveyor belts which convey the rolling trucks to the individual stations. The bottom of the rolling truck is then in direct contact with the conveyor belt. The area in which the bottom of the rolling truck contacts the conveyor belt is known as the contact area. This contact area must be absolutely smooth, as it is subject to stresses due to the conveyor belt and the weight of the rolling truck. With the known rolling trucks, the transponder is embedded inside the contact area in a recess in the bottom surface of the truck to provide a smooth surface, and to protect the transponder.
One disadvantage of the known rolling trucks is that the transponder must have a large coil because of the comparatively great distance from the floor and the reader in the floor. This not only increases the dimensions on the whole, but also increases the price of the transponder. One result of the large dimensions of the transponder is that the transponder must be arranged inside the contact area.
Additional costs are incurred because the transponder is located in the contact area of the bottom of the rolling truck. First the bottom of the truck must be specially designed in this area to protect the transponder from the conveyor belt. Finally, the power of the reader must also be high because of the predetermined distance between the transponder and the antenna of the reader installed in the floor.